Metallurgical refractory lining-guided inorganic binder for stable lithium storage in silicon microparticle anodes

Abstract

Silicon is a promising anode material for next-generation lithium-ion batteries (LIBs), offering a significantly higher theoretical capacity than graphite. Although nano-silicon excels, its high cost limits its practicality, making silicon microparticles (μSi) a more economical and scalable alternative. However, μSi anodes are hindered by substantial capacity degradation, resulting from the over 300% volume expansion upon cycling. This study introduces an aluminum dihydrogen phosphate (Al(H₂PO₄)₃, AHP) binder system, designed based on the principles of refractory chemistry, which effectively mitigates interfacial instability and mechanical failures in μSi anodes. The water-soluble AHP binder forms a uniform electrode through in situ dehydration condensation, creating a covalently cross-linked inorganic network. This high-modulus cross-linked network restricts the expansion of μSi particles during cycling, thereby preserving electrode integrity. As a result, μSi anodes incorporating the AHP binder exhibit exceptional cyclability, retaining a capacity of 1300.4 mA h g⁻¹ after 200 cycles at 0.5 A g⁻¹, alongside impressive rate capabilities of 936.4 mA h g⁻¹ and 769.1 mA h g⁻¹ at 4 A g⁻¹ and 5 A g⁻¹, respectively. Additionally, the AHP binder demonstrates superior compatibility with lithium iron phosphate (LiFePO₄, LFP) cathodes. This work establishes inorganic binders as a practical and economical solution for high-performance μSi anodes, enhancing energy density and lifespan of LIBs.